Heater Wire Gauge

  • I wired up my heater block leads to some high temp wire I had handy, which I think is 18 or 16awg, but this is too thick to fit into my DuetWifi screw terminal. Is there a recommended awg for a 24v 50w heater? Can I just solder a short length of proper sized wire to get it to fit in the terminal, or would that violate that "no tinning the ends" rule I read about?

  • What you need are "boot lace" terminals, and the crimping tool to suit.

    If you solder a thinner wire on the end of the heater wire, you negate the need for the thicker wire and yes you then have a solder joint in the line. It's only a couple of amps, so you're not going to melt it, but it's still not ideal.

    I(A) = P(W) / V(V)

    I = 50/24 = 2.1A

    So 16AWG would be the one according to my chart.

    Seriously, if you're building printers or doing anything like that, a bootlace ferrule kit and crimpers should be in the box.

    Hope that helps (and that I am correct, please double check).

  • Here is another chart which indicates that 22 or 24 AWG would suffice for 2.1 Amps https://www.engineeringtoolbox.com/wire-gauges-d_419.html

  • Using silicone or even fiberglass reinforced silicone insulated wire you can exceed the "normal" ratings that are usually for PVC as the insulation can handle more heat. (i.e. they have their own rating tables)

    Ferrules or other suitable crimp terminals cannot be understated like corexy points out.

  • Thanks for the help! I ordered ferrules and a crimper. Can anyone confirm if a 16awg ferrule would fit in the heater terminal? Sounds like it would still be too big.

  • 16 ga is seriously too heavy a wire for this application! The thickest I would go to is 20 ga. My preference would be 22 ga.

  • I extended my bed heater wires (~10A current draw) with silicone 18 awg wire although they are out of the enclosure. They get a bit hotter than ambient (~15 degrees) when printing abs for longer periods and that is ok even for pvc insulated wires.. When the wires will be very close to very hot regions you should oversize the wires a bit since the resistance changes so in my case 14AWG wire is powering the bed inside the enclosure (although 16 would have been just fine really). You should take care that you make good connections when extending wires and if you solder them take care that you dont put high mechanical stress on soldered spot.

    Note that your hotend wont be pulling 2A all the time and PID will keep the wires cooler than bang bang mode (same is true for PID bed control).

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